Evolutionary relationship analysis of Middle East respiratory syndrome coronavirus 4a and 4b protein coding sequences

The 4a and 4b proteins of the Middle East respiratory syndrome coronavirus (MERS-CoV) have been described for their antagonism on host innate immunity. However, unlike clustering patterns of the complete gene sequences of human and camel MERS-CoVs, the 4a and 4b protein coding regions did not constitute species-specific phylogenetic groups. Moreover, given the estimated evolutionary rates of the complete, 4a, and 4b gene sequences, the 4a and 4b proteins might be less affected by species-specific innate immune pressures. These results suggest that the 4a and 4b proteins of MERS-CoV may function against host innate immunity in a manner independent of host species and/or evolutionary clustering patterns.